Litz Wire 102: What grade of magnet wire is right for your Litz wire application?

When designing or selecting a Litz wire conductor for use in a winding, it is important to consider which grades of Litz wire are likely to be the most appropriate for your application. Not all Litz wires are created equal, and different grades of magnet wire can offer a variety of advantages and desired properties when used for the strands of a Litz wire conductor. Some things to consider when selecting a magnet wire grade can include the temperature rating needed, cost, solderability, expected thermal life, abrasion resistance, and partial discharge resistance.

• Temperature Rating: NEMA MW 1000 covers magnet wires with temperature ratings from 105°C to 240° Some manufacturers’ product offerings go even further and claim temperature ratings of 260°C or more. The magnet wire grade selected for a given application should be appropriate for the operating temperature.
• Cost: At each step up in temperature rating, there is also an associated increase in the price of the magnet wire. Those increases may put the higher temperature grades, like MW 82-C, MW 35-C or MW 16-C, out of reach for some cost-sensitive applications.
• Solderability: The easiest way to remove the enamel layer from the ends of a Litz wire conductor for termination is to solder the ends of the Litz wire conductor. Most of the commonly used magnet wire grades with temperature ratings of up to 180°C are solderable, including MW 80-C, MW 79-C, MW 77-C, MW 82-C, and MW 83-C. Magnet wires with temperature ratings over 180°C, such as MW 35-C and MW 16-C are not solderable, and additional steps are required to remove the enamel from the strands of Litz wires made using those grades. Required solder bath temperatures can also vary by magnet wire grade. For more on this subject, consult Rubadue’s Termination Guide for Litz Wire Conductors. Termination Guide for Litz Wire Conductors | RubadueWire
• Expected Thermal Life: Magnet wires are rated for a minimum expected operating life of 20,000 hours at their rated temperatures. If the desired or required operating life for your product is greater than 20,000 hours, then a higher temperature enamel may be something to consider when designing the windings.
• Abrasion Resistance: When harsh processing conditions are present in the winding process, abrasion resistance can be an important consideration when selecting a Litz wire for your application. See tables 1 and 2 below for a general comparison of various NEMA magnet wire grades. Heavier enamel builds and/or added overall coverings, such as single or double nylon serves, should also be evaluated when abrasion during the winding process is a potential concern. For more information on served Litz, consult our tech blog post on textile served Litz wires. Litz Wire 101: When is a textile serve appropriate for your application? | RubadueWire
• Partial Discharge Resistance: For inverter-driven applications, where windings may be subjected to higher voltage spikes, partial discharge (PD) resistant magnet wire may need to be considered and/or evaluated for use in your application. Examples of PD resistant magnet wire product offerings on the market include Essex Furukawa’s Ultrashield® Plus and REA Magnet Wire’s NanoShield SD. PD resistance is not a requirement of NEMA MW 1000, meaning that such products exceed NEMA MW 1000 requirements and will need to be specified by name rather than by NEMA grade, when such products are required.

Below are two tables comparing several common magnet wire grades.

Table 1: Solderable Magnet Wire Grades

* Based on minimum scrape resistance requirements per NEMA MW 1000.

Table 2: Non-Solderable Magnet Wire Grades

* Based on minimum scrape resistance requirements per NEMA MW 1000.

Need further assistance with determining what magnet wire grade and build is appropriate for your Litz wire product and application? Contact our knowledgeable sales and engineering teams to discuss your application at sales@rubadue.com or +1(970) 351-6100.